<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="./js/jquery.js"></script>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      .box {
        width: 100px;
        height: 100px;
        background-color: red;
      }
    </style>
  </head>
  <body>
    <button>添加类</button>
    <button>删除类</button>
    <button>切换类</button>
     <div class="box"></div>
    <script>
       $(function(){
      $("button").click(function(){})
           

       })
    </script>
  </body>
</html>
